Abstract : The report presents a simple method of determining the tritium content in the air in the vicinity of an open tank of tritiated water. Psychrometric measurements to determine absolute humidity are substituted for volumetric measurements of air and water samples. The report includes an extensive series of tables to facilitate computations. The tables give the amount of water in micrograms per milliliter of air mixture for various wet and dry bulb temperatures from 35F to 114F. Successive tables are included for each inch of barometric pressure from 22 inches to 32 inches Hg. With the tritium analysis results in microcuries per gram of water, a simple multiplication gives the result in microcuries of tritium per milliliter. (Author)